Can. 1526 §1. The burden of proof rests upon the
person who makes the allegation.

§2. The following do not need proof:

1/ matters presumed by the law itself;

2/ facts alleged by one of the contending parties
and admitted by the other unless the law or the judge nevertheless requires
proof.

Can. 1527 §1. Proofs of any kind which seem useful
for adjudicating the case and are licit can be brought forward.

§2. If a party insists that a proof rejected by a
judge be accepted, the judge is to decide the matter as promptly as possible (expeditissime).

Can. 1528 If a party or a witness refuses to
appear before the judge to testify, it is permissible to hear them through a
lay person designated by the judge or to require of them a declaration either
before a notary public or in any other legitimate manner.

Can. 1529 Except for a grave cause, the judge is
not to proceed to collect the proofs before the joinder of the issue.